[35.06] A Deep New CCD/Objective-Prism Survey for Emission-Line Galaxies

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We describe our new digital objective-prism survey for extragalactic
emission-line objects. Our international collaborative effort initiated
observations in March 1994 on the 0.61-m Burrell Schmidt telescope located
at KPNO. The technique we employ combines
the benefits of a traditional photographic objective-prism survey with
the advantages of using a CCD detector. We will select emission-line
galaxy candidates primarily by their [O III]$\lambda$5007 and/or H$\beta$
lines, similar to familiar line-selected samples such as the UM, Case,
and Second Byurakan surveys. However, we expect to be sensitive to galaxies
with continuum magnitudes as faint as B = 20 -- 21, much deeper than any
existing surveys. In addition to providing much higher QE and larger dynamic
range compared to photographic plates, CCDs have the added advantages for
our survey of delivering digitized spectra which will allow for automated
object selection, as well as providing the ability to determine the selection
characteristics and completeness limits of the sample directly from the
survey data. The field of view of our CCD is 1.1$^\circ$ square, and the
prism employed delivers 19 \AA /pixel at 5000 \AA. The spectral range covered
(4800 -- 5500 \AA ) is restricted by a special filter developed for this
project that excludes the strong night-sky line at 5577 \AA. This
arrangement greatly reduces the sky background while still providing
coverage out to z = 0.10 for the strong [O III]$\lambda$5007 line and to z =
0.14 for H$\beta$. Our initial pilot project
covers 100 square degrees and overlaps the CfA Century Redshift Survey in the
north Galactic cap. We anticipate extending the survey to cover large areas
of both Galactic caps in the future. Examples of objects discovered in our
initial semester of observations will be presented, along with an assessment
of the depth and reliabilty of the survey technique. Our scientific
goals for this survey include a more accurate determination of the luminosity
function and spatial distribution of AGN and actively star-forming galaxies.